Ship propulsion



BEST AVAILABLE COPN Feb. 22', 1927. E. JEWITT SHIP EROPULS I ON Filed May 1, 1925 2 Sheets-Sheet 1 Fig! Inve rmor:

wfiv e o m L @Mm n n H DUQ IO.

SEST AVAI LABLE COP\ 1,618,827

Feb; 22 1927.

D. E. JEWITT SHIP PROPULSION Filed May 1, 1925 2 Sheets-Sheet 2 Inventor;

i w/n B? E t s n m A MW DHH b UNITED STATES BEST AVAILABLE com PATENT OFFICE.

DENNIS ERNEST JEWITT, OF OLD BILTON, NEAR RUGBY, ENGLAND, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

SHIP PROPULSION.

Application filed May 1, 1923, Serial No. 636,005, and in Great Britain June 21, 1922.

My invention relates to systems of ship propulsion, and especially to systems of elec tric ship propulsion wherein a propeller is driven by motors supplied with current from one or more direct current generators driven by prime movers such as Diesel engines or steam turbines, and ,wherein means are provided'for preventing injury to the apparatus.

The propelling equipment of an electrically driven ship is usually designed for maxi mum efliciency under normal operating conditions but must also be able to withstand the comparatively severe but infrequent strain occasioned by maneuvering. Such equipment, especially in the case of the smaller vessels, is often under the control of unskilled operators and it is desirable to provide controlling apparatus which will automatically prevent the operator from doing something which may damage the electrical or other equipment. Simplicity in the 0 eration of the control apparatus is there ore very desirable. In accordance with my invention a single handwheel or lever is used to control the operation of the equipment, and means responsive to abnormal conditions in the system are utilized to vary automatically the circuits to prevent damage.

An object of my invention is to provide automatically operated means for preventing injury to the propelling equipment under abnormal operating conditions.

A further ob]ect is to provide means for automatically limiting the load current to a safe value during acceleration in either direction.

A further object is to provide means for preventing overloading during deceleration when the main motor is being driven by the propeller as a generator.

A further object is to provide means through which the propeller motor may be operated continuously at any speed between maximum and standstill.

A further object .is to provide. means for efiiciently and effectively operating all or any part of a number of generators arranged to supply current to a single load motor.

My invention will be better understood from the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claims. 7

Referring now the drawings, Fig. 1

shows the application of my invention to a system of ship propulsion comprising a singlemain motor supplied with current from a slngle generator; Fig. 2 shows the use in connection with a system comprising a plurality of generators arranged to supply a single propeller motor; and Fig. 3 shows certain details of the equipment through which operation of the systems illustrated by Figs. 1 and 2 is controlled.

Fig. 1 shows a propeller motor 1 provided with it separately excited shunt field winding 2 and arranged to be supplied with current from a generator 3 driven by any suitable prime mover such as a Diesel engine (not shown). The generator 3 is provided with a shunt field winding 4 arranged to be energized from a suitable source of direct current 5 through a reversing potentiometer 6 which is adapted to regulate the amount and direction of the generator exciting current and is operated by electrodynamic means shown as a pilot motor 7 acting through worm 8, insulating disk 9, sprocket gears 10 and 11 and chain 12 to rotate the control arm 13 in either direction. The speed and direction of rotation of the gen orator 3, and consequently the propellor motor speed and direction of rotation, are determined by the position of the control arm 13. otthe potentiometer 6. As shown in Fig. 1, the arm 13 is in a position to give zerovoltage across the terminals of the generator field winding 4.

As shown by Figs. 1 and 8, a single control lever 1 1 is provided for controlling the ship. .Attached to and insulated from the lever 14: are brushes 15 and 16 connected to the direct current source 5 and arranged to cooperate with a follow-up device consisting of insulating disk 9 and rotatable conductive segments 17 and 18 which are mounted upon this disk and function as a reversing switch in the circuit between the source 5 and the commutator of the pilot motor 7. The segments 17 and 18 also serve to reverse the polarity of the voltage impressed on the shunt coil 19 of the overload relay 20, this coil being connected to the source 5 in parallel with the armature of the pilot motor.

, Connected in series with the armature of the pilot motor 7 is a resistor 21 which serves the double purpose of limiting the armature current to a safe value at starting and regulating the speed atwhich the pilot motor is driven to operate the1-potentioineter 6 andthe motor field rheostat 44 see Fig. 2). The normal value of the pilot motor armature current isdetermined by the setting of contact 22. The resistor-21B also provided with a contact 23 the purpose of which is hereinafter explained. If difiiculty isfound in regulating thepilot, motor speed and at the same time limiting the armature current to a. safe value by means of the resistor 21, a resistor 24 may be provided in the field circuit. or the pilot motor for the purpose of speed control. Ineither case the steady runn ng current of the pilot motor 7 should be adjusted to give maximum permi sible acceleration of the propeller motor 1 under tineweather and light draught conditions.

Mounted upon the lever 14 is an insulated brush 25 connected to one terminal otthe source 5 and arranged to cooperate with the stationary segments 26 which are cross connected-with like segments 27. A brush 28 mounted uponthe rotatable insulating disk 9- is' arranged to cooperate with the segments 27 for the purposev of connecting the coil 29- of the relay 30 to the source 5 through brush 25,:segments 26, segments 27, brush 28 and eithershunt relay 31 or brush 32 whlch 1nterconnects contacts to close the circuit when the: potentiometer is in a position to give zeroi voltage upon the generator field coil; 4.- In" the. off position of the lever 14. and whenthe propeller: motor is 'started' fromrest-in either.- directionythe connection of the coil 29- with the source 5 is main tained and the brake resistance, 33-is short: circuited by the .relay 30. Upon sudden movement of the lever. 14 from. full speed ahead to full speed astern, or viceversa', the brush 25ris moved onto a segment 26] not connected to the segment 27 which is at that instant in contact witlrbrush 28, and the circuit to the coil 29v iszbroken thereby inserting the brakeresistance 3?: in themain circuits and short-circuiting a part of theresistor: 21 through contact;- 23 ,to accelerate the speedat which the pilot motordrives: the arm l3 ofthe potentiometer. ,VVhen the arm 12-3; hasmoved to its illustrated zero voltage position, the insulated conductive brush is caused to interconnect the contacts35 whereupon the brake resistance is again short-circuited and the generator 3 is brought to'rest and accelerated in the opposite direction at the normalrate.

A shunt relay 31 havingv coil34 connected across-the brake resistor 33 is provided" for thepnrpose of preventingiclosure of the circuitto coil 29 until the main load current has decreased to a predeterminedval-ue orj untilthe voltage impressedonthe generator field has been reduced to zero A reverse powerrelay 36 having coils 36' and. 37 is provided for the purpose of intcrrupting tlie 15187827 BEST AVAILABLE COP\ armature circuit of the pilot. motor during brakingjitan excessive amount of power is supplied to the generator 3 by the motor 1 driven by the propeller as a generator.

This relay is always closed-when power is beingsuppliedfrom thegenerator 3 to the nip-tor 1 Also in the armature circuit of th'e"pilot'motor is an overload relay 20 provided with shunt coil 19 and series coil 38 and arranged to prevent too rapid acceleration of the propeller motor in either direction when power is being. supplied from generator to motor 1. The magnetic polarity or" the shunt and series coils of relay 20 should be such that when air-accelerating. current is passing from generator 3 to motor 1 both coils ai'eacting. in conjunction.

Fig. 2 shows a system in which foursepa=- rately driven generators 39 are connected so that they may each or. all supply current to the propeller motor 1;. and in which each generator is provided with an armature short-circuiting switch 40 adapted to. be closed when the engine driying the generator is out of operation. In the circuit; of each field winding 41 is connected a three pole switch 42 to permit opening of the, field circuit before the engine is stopped and before the corresponding short circuiting switch 4Q is closed. The left'hand and center. blades of the field switches 42 serve to conneCt the generator field terminals. to. the potentiometer 6 The right'hand blade connects a separate field resistor 43 in parallel with. the motor field rheostat 44 for the purpose. of accommodating the motor field voltage to the. change in thenumber of gen erators supplying power to it. The arm 45 of the motor, field 'rheostat 44-'isarrange d to rotate. simultaneously with, and in the sam direction aswthe, ar'nrof the potentiometer 6 to whichit may be connected in any suitable manner. I rIEig, 2 contacts, 35 andthe short-circuitingbrush 32 aren' ounted upon the motorfield rheostatinstead ot on the potentiometer 6 as in Fig. 1. Discharge resistors 46 are provided for each generator field so asto allow of one generator being unloaded without interrupting tlie total power supply. Reverse power relays 47 are provided in each v generator circuit. Suitable switches 49 and 50 may be. provided in the field circuits of the motors 1 and 7 respectively. The arm of the motor field rheostat 44 moves along with the arm 13 of the, potentiometer 6 but does not regulate the motor field until. full field'has been applied to all the generators. This permits s'peed'variation of. the propeller motor under control of the pilot motor which is prevented by the overload relay 20 from changing either the motor or generator excitation in sucha way a s'to produce excessive current in the main power circuit.

In operating the propeller from rest to 1,618,827 BEST AVAILABLE COP\ full speed ahead, the operator moves the lever 14 from the off position in which it is shown .to the full speed ahead position, shown in dotted lines, thereby interconnecting the source and the pilot motor 7 through brush 15, segment 17, contacts of relays 20 and 36, resistor 21, contact 22, armature of motor 7, segment 18, and brush 16. The motor begins to move and will continue to run until it has moved the rotating disk 9. to a position corresponding to the position of 'the control lever where it will open its own armature circuit through the disengagement of brushes and 16 with segments 17 and 18 and stop. Rotation of the insulating disk 9 causes a corresponding movement of the potentiometer arm 13 and thus gradually increases the exc ting current of the generator 3. If for any reason the main power current tends to rise above asafe value, the overload relay 20 is operated to interrupt'the pilot motor armature circuit and stop movement of the potentiometer arm 13 until the current has fallento a safe value when relay 2O closesto re-establish the circuit ofthe pilot :motor which then operates the potentiometer arm 13 to increase the exciting currentof the generator or generators to full value. If the motor field rheostat is connected as shown in Fig. 2, further operation of the pilot motor will operate to rotate the arm45 to increase the resistance ofthe propeller motor field circuit. In starting the propeller from rest to full speed astern, the operation is the same as that just described except that the lever 14 is moved to the astern position shown in dotted lines thereby starting the pilot motor in the reverse direction. If the lever 14 is stopped at any position intermediate the off and ahead or astern positions, the pilot motor will rotate the disk 9 to a position corresponding to the position of the lever when the segments 17 and 18 will be moved out of contact with the brushes 15 and 16 and the armature circuit of the pilot motor will be interrupted. This makes it possible continuously to operate at any desired speed.

When it is desired to go from full speed ahead to full speed astern, the control lever is moved to the astern position. Movement of the lever 14 to off position starts rotation of the pilot motor '7 through the circuit previously traced and itcommences to slow up the propeller motor first by decreasing the resistance in the motor field circuit through movement of the motor field rheostat and then by reducing the generator volt-age through continued rotation of the potentiometer arm 13. During this movement the rate of deceleration is controlled by the speed of the pilot motor 7, the circuit of which is immediately interrupted by the reverse power relay 36 if the power returned to the generator or generators is too great for the engines to dissipate safely. It the control lever 14 passes the OE position before the rotating disk 9 has had time to reach a corresponding position, the circuit from source 5 through the contacts of relay 31, coil 29, brush 28, segments 26 and 27, and brush 25, ba'ck'to source 5 which interconnects the source 5 and coil 29 of the solenoid 30 is interrupted-due to'the fact that the brush is movedonto the stationary segment 26 not interconnected with the segment 27 with which the brush 28 is at this instant in contact. The relay thereupon moves to its lower position introducing the brake resistance 33 into the main circuit and 'short-circuiting the part of the resistor 21 between its left-hand terminal and the contact 23, thereby accelerating the speed of the pilot motor and increasing-the rate at which the excitation of the generators is decreased. hen the arm 13 has been moved to zero voltage position,-all the energy is being dissipated in the ohmic resistance of the main circuit and the brake resistor may be short circuited. This is accomplished in the zero position of the arm 13 by the brush 32 which interconnects the cont-acts 35 to close the circuit of coil 29 from the plus side of source 5, brush 32, and contacts 35, coil 29, brush 28, both of the segments 26 and 27 (the brush being wide enough to make contact with both segments by bridging the gap separating the two), brush 25, back to the other side of the source and operate the relay 30 from its lower to its upper position thereby increasing the resistance in the pilot motor armature circuit and short-circuiting the brake resistor 33. Due to the short-circuiting of the brake resistor 33, the coil 34 ofthe shunt'relay 31 is de-energized and the coil 29 of the relay 30 is interconnected with the direct current source 5 through brush 25, segments 26 and 27 brush 28 and relay 31. The relay 30 is thus positively closed as the arm 13 of the potentiometer passes through the zero voltage position. The final stopping of the propeller and its acceleration in the opposite direction is thereafter effected with the pilot motor operating at its normal speed. The generator excitation is thus changed at a comparatively low rate during acceleration of the propeller motor and at a comparativelyhigh rate during deceleration of the propeller motor.

The shunt relay 31 serves both to insure positive short-circuiting of the braking resistor when the potentiometer arm 13 passes through the zero voltage position during deceleration of the propeller motor and also to short circuit this resistor 'whcn the current in the main circuit has decreased to a predetermined value.

In order to insure safely shortcircuiting of the braking resistor in case the operator Hit) momentarily brings the control lever from fullspeed ahead'position into reverse. posi-. tion and. then quickly-back to the full speed ahead position before the pilot motor. has time to fully respond to the movement, th. relay 31 should be adjusted to close as soon as the power current passing through the braking resistor is low enough to prevent the flow 0t unduly large circulating currents in the power system. The relay 31 together with the brush 32 and the contacts 35 thus control the relay to short circuit the braking resistor at a comparatively high value of decelerating current and to perform a like function at the con'iparatively low value of power current.

\Vhat I'claim as new and desire to secure by Letters. Patent of the United States,

1. A system ofship propulsion wherein a propeller motor is arranged to be supplied with power from a direct current generator, comprising a single manually operated means for controlling the operationof said system, and automatic means responsive to; movementj f said manual means for changing the exeitation of said generator at a predetermined rate duringthe acceleration of said propeller motor and for changing the excitation of said generator. at a different' predetermi ned rate during deceleration of said'propell er motor. I

2. A system of ship propulsionwherein a propeller motor is arrange'd to be supplied with power from a. direct current generator, comprising a single manually operated means for controlling the operation of said system, and automatic means responsive to movement of said manuahmeans for changing the excitation of'said generator at a. predetermined rate during the acceleration of said propeller motor and for changing the'excitati onof said generator at a 'difi'er ent predetermined rate during deceleration. of said propeller motor and for changing the excitation of' said propeller motor at a predetermined rate when the excitation of said enerator is at its maximum value.

'K'system of ship propulsion wherein a propeller motor'is arranged to be supplied. with power from a direct current generator, comprising 'a single manually operated means for controlling the operation of said system, and automatic means responsive to movement of' said manual means for changing the excitation of said generator at a predetermined rate during the acceleration of said propeller motor and for changing the excitation of said propeller motor at a predetermined rate after the excitation of said generator has been increased to its maximum value.

4Q In a system of ship propulsion wherein a propeller motor is interconnected with a generator by a power circuit adapted to conduct current between said motor and BEST AVAILABLE COP.

said generator and wherein a braking resistance is arranged to be inserted in said circuit, comprising manually operated means for controlling the operation of said system, and automatic means responsive to movement of said manual means for changing the field current of said generator at a predetermined rate while accelerating said propeller motor and for inserting said resistor in said circuit and decreasing. the field current of said generator at a ciii'erent predc tcrmined rate while decelerating said propeller motor.

A system of ship propulsion wherein a propeller motor is interconnected with a generator by a power circuit adapted to conduct current between said motor and said generator and wherein a braking resistance is arranged to be inserted in said circuit, comprising manually operated means forcontrolling the operation of said system, apotentiometer. for controlling the direction and value of. the generator field current, electrodynan'iic means responsive to one movement of. said manual means for operating the potentiometer. in one direction at a comparatively low predetermined rate of speed, and'automatic means responsive to movement of said manual means in another direction for inserting said braking resistance in said power circuit andaltering the operating characteristics of said electrodynamic means to cause the same to operate said potentiometer in the opposite direction at a comparatively high predetermined rate of speed.

- 6. A system of ship propulsion wherein a propeller motor is interconnected with a generator by a power circuit adapted to conduct current between said motor and said generator and wherein a braking resistance is arranged to be inserted in said circuit, comprising manually operated means for controlling the operation of said system, a potentiometer for controlling the direction and value of the generator field current, electrodynamic means responsive to one movement of'said manual means for operating the potentiometer in one direction at a comparatively low predetermined rate of speed, a relay responsive to movement of said manual means in another direction for inserting saidbraking resistor in said power circuit and altering the operating characteristics ofsaid electrodynamic means .to cause the same to operate said potentiometer. in the opposite direction at a comparatively high predetermined rate of speed, and means responsive to movement of said electrodynamic means into a position corresponding to the zero voltage position of said potentiometer for causing said relay to short circuit said braking resistor and restore the first operating characteristic to said electrodynamic means.

7. A claim according to claim 6 characterized by the fact that an overload relay is provided in said power circuit for the pur- I pose of rendering said electrodynamic means inoperative when the current flowing between the generator and motor exceeds a predetermined value.

8. A claim according to claim 6 charac terized by the fact that a reverse power lay is provided in the main power circuit for rendering said electrodynamic means inoperative when the power transmitted from said motor to said generator exceeds a predetermined value.

9. A power system wherein a load motor is arranged to be supplied with power from a plurality of generators, comprising a single manually operated means for controlling the operation of said system, automatic means responsive to movement of said manual means arranged to increase the field excitation of said generators at a comparatively low predetermined rate during the acceleration of said load motor and to decrease the excitation of said generators at a comparatively high predetermined rate during the deceleration of said load motor and to change the excitation of said motor at a predetermined rate only when the excitation of said generators is at a maximum value, and means for adapting the value of the motor exciting current to the number of generators connected in series with said motor.

10. The method of reversing the propeller motor in a system of ship propulsion which consists in increasing the resistance of the system, reducing the system voltage at a comparatively high rate of change, decreasing the resistance of the system, reversing the polarity of the system voltage, and increasing the system voltage at a comparatively low rate of change.

11. A power system wherein a load motor is interconnected with a generator by a power circuit adapted to conduct current be tween said motor and said generator and wherein a braking resistor is arranged to be inserted in said circuit, comprising manually operated means for controlling the operation of said system, a potentiometer for controlling the direction and value of the gen erator field current, electrodynamic means responsive to one movement of said manual means for operating said potentiometer in a direction to accelerate said load motor at a comparatively low predetermined rate of speed, a relay responsive to movement of said manual means in another direction for inserting said braking resistor in said power circuit and altering the operating chagacteristics of said electrodynamic means to cause the same to operate said potentiometer at a comparatively high predetermined rate of speed in a direction to decele ate said load BEST AVAiLABLE CQPi motor, a brush arranged to close the exciting circuit of said relay upon the movement of said electrodynamic means into a position corresponding to the zero voltage position of said potentiometer whereby said relay is caused to short circuit said braking resistor and restore the first operating characteristics of said electrodynamic means, and a second relay arranged to close the exciting circuit of said first mentioned relay upon the decrease below a predetermined value of the current flowing in said power circuit and also arranged to maintain the exciting circuit of said first mentioned relay closed after it has been closed by movement of said brush into a position corresponding to the zero voltage position of said potentiometer.

12. In a direct current ship propulsion system, a propeller motor arranged to be driven by the propeller as a generator when decelerating the ship, a generator for supplying current to said motor, means adapted to be operated to vary the generator field current gradually from zero to maximum in either direction, means comprising a pilot motor for actuating said excitation controlling means, a relay for controlling the operation of said pilot motor comprising a winding in series with said generator and motor, said relay being arranged to interrupt the operation of said pilot motor whenever the current flowing in the circuit connecting the generator and motor exceeds a predetermined valne in either direction, and means responsive to the current and voltage in the system for controlling the operation of said pilot motor whenever the power developed by said propeller motor operating as a generator exceeds a predetermined value.

13. A direct current ship propulsion system comprising a. motor arranged to drive a propeller, a generator for supplyin current to said motor, means for grac ually varying and reversing the generator excitation, means comprising a pilot motor for operating said excitation controlling means, a. braking resistor connected in series with said generator and motor, means for controlling the speed of the pilot motor, and means arranged to close a shunt circuit around said resistor and to control said pilot motor speed varying means whereby the speed 01 the pilot motor is increased upon the opening of said shunt circuit.

14. A direct current ship propulsion system comprising a motor arranged to drive a propeller, a. generator for supplying current to said motor, means for gradually varying and reversing the generator excitation, means comprising a pilot motor for operating said excitation controlling means, a braking resistor connected in series with said generator and motor, means for controlling the speed of the pilot motor, and a winding the circuit of which is controlled by the operating means of said generator excitation controlling means for controlling the connection of's'aid braking resistor and the speed of said pilot motor.

15. A direct current ship propulsion system wherein a propeller motor is arranged to be supplied with current from agei'ierator under normal operating conditions and to be driven by the propeller when its direction of rotation is being reversed and wherein means for varying and reversing the generator field current are operated by means comprising a. pilot motor, characterized by the fact that means are provided whereby said pilot motor is driven at a. relatively low speed when said generator is supplying current to said motor and at a. relatively high speed when said motor is being driven by the propeller.

16. In a power system, a load motor arranged to be driven by its lead as a genera.-

tor when decelerating, a generator for sups my hand this thirteenth day of April, 1923.

relay being arranged to interrupt the operation of said electrodynamic means when ever the current flowing in the circuit connecting the generator and motor exceeds a predetermined value in either direct-ion, and means responsive to the current and voltage in the system for controlling the operation of said electrodynamic means whenever the power developed by said load motor operating as a generator exceeds a predetermined value.

17. In a power system, a load motor arranged to be driven by its load as a generator when oecclerating, a generator for supplying current to said motor, a braking resistance arranged to be inserted in said circu'1t,n'iar;ually operated means for controlling the operation of the system, and automatic means responsive to m vement o't' .ltlltl mauual means for changing the tield current of said generator at a, predetermined rate while accelerat ng said load motor and for insertrng said resistor in said circuit and "decreasing the lield current of said generator at a diii'er'ent'predetermined rate while decelerating said load motor.

in witness whereof, I have hereunto DENNIS ERNEST JEWltll'l. 

